Transplant production system

ABSTRACT

A system for transplant production comprising: at least one air conditioner installed in a completely light shielding closed structure surrounded by a thermally insulated wall, the air conditioner controlling the temperature and humidity of air in the closed structure; at least one box-shaped culturing module disposed in the internal space of the closed structure, the culturing module having a front face opening which is opened to the internal space of the closed structure; a plurality of transplant production shelves arranged vertically in multi-layer in the culturing module to form a transplant production space between the upper and lower transplant production shelves; a plurality of plug trays for holding a plant growing medium mounted on each transplant production shelf; a sub-irrigation unit capable of irrigation from the bottom of the plug trays mounted on each transplant production shelf; an artificial lighting unit provided on the back of each transplant production shelf, the artificial lighting unit irradiating light to the lower plug trays; and at least one air fan fixed to the back wall of each transplant production shelf of the culturing module. By sucking the air whose temperature and humidity have been controlled by the air conditioner using the air fan from the front face opening of the culturing module and sending the air to the rear of the back wall of each transplant production shelf, temperature-controlled and humidity-controlled air can be effectively generated.

TECHNICAL FIELD

The present invention relates to a system for transplant production withmulti-layer shelving in a closed space. More specifically, the presentinvention relates to a transplant production system using an artificiallight source, an air conditioner and an automatic irrigation unit andcapable of realizing a stable transplant production environment notinfluenced by an external environment and efficiently producinghigh-quality plug seedlings under a uniform growing condition.

BACKGROUND ART

Conventionally, as a method for growing seedlings of various plants,there is a transplant production method represented by a plant factory.This transplant production method is a method for stably growinghigh-quality uniform seedling through labor-saving at a low cost byusing a closed-type transplant production system including an artificiallight source, air conditioner and an automatic irrigation unit tothereby artificially control the light quantity, temperature, humidity,wind speed and irrigation quantity in a transplant production space tooptimum states.

As this type of closed-type transplant production system, an artificialenvironmental system is disclosed in Japanese Patent No. 3026253. Inthis system, an air conditioning chamber is formed at the inside of aceiling wall of a box-shaped outer chamber constituted by a thermalinsulating material, a blowing chamber and a suction chamber are formedat the inside of the opposed side walls of the outer chamber,respectively, and transplant production boxes are removably disposed ina multi-layer manner between the blowing chamber and the suctionchamber. The air in the system is blown into a transplant productionspace from a honeycomb-structural wall of the blowing chamber and suckedby passing through a porous-plate wall of the suction chamber, and sentto the blowing chamber again by passing through a ventilation flue inthe air conditioning chamber to thereby circulate the air. Thecirculation air is adjusted in temperature and humidity by an airconditioner and blower positioned in the air conditioning chamber andcirculated. However, in such a system described above, since the airconditioning chamber, the blowing chamber and the suction chamber areformed at the inside of the outer chamber, there is a problem that theutilization efficiency of the transplant production space in the outerchamber is deteriorated. Also, since special rectifying means foruniformly blowing air from the blowing chamber is used, the structure ofthe system becomes complex.

Moreover, as an automatic irrigation unit used for this type oftransplant production system, there is a unit disclosed by a reportentitled “Development of an injection type sub-irrigation unit for plugtray” presented in the joint meeting of three scientific societies ofThe Society of Agricultural Meteorology of Japan, Japanese Society ofEnvironment Control in Biology and Japanese Society of High Technologyin Agriculture in 1999. The automatic irrigation unit reported hereinjects proper amounts of water and a culture solution to a culturemedium for a short time by inserting a plurality of nozzle into a plugtray from the bottom holes thereof. This irrigation unit has a featurethat excess water or excess culture solution is not discharged becauseinjected water does not leak from the bottom holes of the plug tray. Itis necessary in such a irrigation unit, however, to prepare a largenumber of nozzles to be inserted into all of the bottom holes formed onthe bottom walls of tens to hundreds of plugs for a single plug tray,mechanically insert these nozzles into all of the bottom holes, and theninject an equal amount of water from each of these nozzles. Thus, inorder to realize these requirements, there is a defect that a complexand expensive mechanism is required.

Further, as another automatic irrigation unit, there is a unit disclosedby a report entitled “Simplification of an automatic irrigation unit onthe basis of evapotranspiration measurement of plug seedlingspopulation” presented in the joint meeting of The Society ofAgricultural Meteorology of Japan and Japanese Society of EnvironmentControl in Biology in 2000. In this automatic irrigation unit, an amountof evapotranspiration of a plant body and a culture medium is measuredas a change in seedling population weight for each plug tray by placingthe plug tray on a pan balance, a switch contact point is set to apointer of the balance, and the switch contact point directly detectsmovement of the pointer to designate start of irrigation to the seedlingpopulation. This unit has a feature that irrigation using a properamount of water can be conducted without discharging excess water, sinceirrigation is started on the basis of the amount of evapotranspirationand irrigation using a minimum necessary amount of water is carried outby using a subtimer. However, this report reveals that, since theoperation of the pointer has a mechanical resistance and movement of thepointer is directly influenced by gravity, the operation of the pointeris incomplete or the operation accuracy thereof has a problem.

Furthermore, Japanese Patent Laid-Open Specification No. 2001-346450discloses a sub-irrigation unit, i.e. a watering unit capable ofwatering from the bottom of a plug tray, for use in a transplantproduction system with multi-layer shelving in a closed space. Thissub-irrigation unit is provided with a shallow quadrangular box havingthree sides surrounded by side walls and having a bottom wall face. Adrainage groove is formed at the side of the box having no side wall. Awater supply pipe is disposed on the side wall face of the side of thebox opposed to the drainage groove. A porous sheet of a synthetic resinis put on the bottom wall face of the box and plug trays are mounted onthe porous sheet. According to the sub-irrigation unit having theabove-described structure, water supplied from the water supply pipe isabsorbed by the porous sheet due to its capillary action and spreads tothe whole of the bottom wall face of the box in a short time to therebyattain a water pool state at a predetermined water level and uniformlysupply water to culture media contained in the respective plugs fromplug holes formed at the bottom of the respective plugs arrayed in theplug tray due to the capillary phenomenon. Since the culture medium ineach plug becomes a water saturated state in a short time due to thecapillary phenomenon, it is not necessary to keep the pool state for along time. However, unless a pump having a large discharge quantity isused, water does not spread to the whole of the bottom wall face of thebox and therefore the pool state is not realized. After irrigation isstopped, water remaining in the porous sheet is discharged to thedrainage groove from an end of the porous sheet hanging down into thedrainage groove. However, since the bottom of each plug contacts withthe porous sheet even after irrigation is stopped, the vicinity of theplug hole is easy to keep a wet state. As a result, roots of seedlingextend to the outside from the plug hole, and therefore a trouble occursin the takeout operation of seedling from the plug, and there is adanger of damaging the roots. To prevent the roots of seedling fromextending up to the vicinity of the plug hole by drying the vicinity ofthe plug hole after irrigation is stopped, it is proposed to form aplurality of small protrusions on the plug bottom so that the plugbottom does not directly contact with the porous sheet. However, asatisfied dry state is not always obtained.

DISCLOSURE OF THE INVENTION

In view of the above circumstances, the inventors of the presentinvention have eagerly studied in order to overcome the above-describedproblems present in the technical field of culturing seedling using aclosed-type transplant production system and provide a transplantproduction technique capable of efficiently producing uniform andhigh-quality seedling at a low energy and a low cost. The presentinvention has accomplished as a result of such studies.

The following are objects of the present invention:

(1) To provide a closed-type transplant production system having a highspace utilization rate in a closed space;

(2) To provide an energy-saving transplant production system capable ofefficiently circulating the air in a closed space by a simple structurewithout using complex rectifying means and capable of realizingeffective temperature and humidity control by minimum necessary power;and

(3) To provide a transplant production system having a sub-irrigationunit requiring only minimum necessary irrigation to culture seedling andcapable of effectively drying the bottom of plug trays when irrigationis stopped.

A transplant production system according to the present inventioncomprises:

at least one air conditioner installed in a completely light shieldingclosed structure surrounded by a thermally insulated wall, the airconditioner controlling the temperature and humidity of air in theclosed structure;

at least one box-shaped culturing module disposed in the internal spaceof the closed structure, the culturing module having a front faceopening which is opened to the internal space of the closed structure;

a plurality of transplant production shelves arranged vertically inmulti-layer in the culturing module to form a transplant productionspace between the upper and lower transplant production shelves;

a plurality of plug trays for holding a plant growing medium mounted oneach transplant production shelf;

a sub-irrigation unit capable of irrigation from the bottom of the plugtrays mounted on each transplant production shelf;

an artificial lighting unit provided on the back of each transplantproduction shelf, the artificial lighting unit irradiating light to thelower plug trays; and

at least one air fan fixed to the back wall of each transplantproduction shelf of the culturing module,

whereby the air whose temperature and humidity have been controlled bythe air conditioner is sucked by the air fan from the front face openingof the culturing module and sent to the rear of the back wall of eachtransplant production shelf to circulate the air in the closedstructure.

It is also possible that a plurality of the culturing modules aredisposed in the internal space of the closed structure so that they arearranged in one line with their front face openings facing to the samedirection.

Alternatively, it is possible that a plurality of the culturing modulesare arranged in two lines with their front face openings in the sameline facing to the same direction, and the front face openings in oneline are opposed to the front face openings in the other line, and awork space and concurrently an air circulation path is formed betweenthe two lines of the culturing modules.

The sub-irrigation unit mounted on each transplant production shelf ispreferably provided with a shallow quadrangular box-shaped irrigationtray having three sides surrounded by side walls and having a bottomwall face, a water supply pipe for supplying water into the irrigationtray is disposed in the irrigation tray, a drainage groove joined to thebottom wall face is formed at the side of the irrigation tray having noside wall, the drainage groove and the bottom wall face are partitionedby a dam, and means for holding a gap between the bottom wall face ofthe irrigation tray and the bottom of the plug tray at the time ofmounting the plug tray on the bottom wall face of the irrigation tray isprovided on the bottom wall face of the irrigation tray.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing an example of a transplantproduction system of the present invention.

FIG. 2 is a schematic longitudinal sectional view showing a flow of airin the internal space of the transplant production system shown in FIG.1.

FIG. 3 is a front view showing an example of a culturing module used forthe transplant production system of the present invention.

FIG. 4 is a side view of the culturing module shown in FIG. 3.

FIG. 5 is a plan view showing an example of a sub-irrigation unit usedfor the transplant production system of the present invention.

FIG. 6 is a perspective view of the sub-irrigation unit shown in FIG. 5.

FIG. 7 is a schematic longitudinal sectional view along the line X-X inFIG. 5.

FIG. 8 is a schematic longitudinal sectional view showing anotherexample of the sub-irrigation unit used for the transplant productionsystem of the present invention.

FIG. 9 is a schematic plan view showing another example of thetransplant production system of the present invention.

FIG. 10 is a schematic plan view showing still another example of thetransplant production system of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferable example of a transplant production system of the presentinvention is described below by referring to the example shown in FIGS.1 and 2. A transplant production system of the present invention is aclosed-type transplant production system constituted by arranging aplurality of box-shaped culturing modules 3, 4, 5, and 6 (four in thecase of the illustrated example) in an internal space of a completelylight shielding closed structure 1 surrounded by a thermally insulatedwall. In the present invention, the closed structure denotes a structurehaving an internal space closed by being surrounded by a wall forcutting off external air temperature and natural light. A typicalstructure is a box-shaped hexahedron obtained by combining reinforcingbars, slates and a thermal insulating material. The external shape ofthe structure is not restricted to a boxy shape. It is allowed to use abarrel shape, hemicylindrical shape or hemispherical shape.

The size of the internal space of the closed structure 1 may bedetermined to proper dimensions depending upon the number of culturingmodules to be arranged in the internal space. In the case of the exampleshown in FIG. 1, two culturing modules 3 and 4 are arranged in one linewith their front face openings facing to the same direction. Inaddition, two culturing modules 5 and 6 are also arranged in one linewith their front face openings facing to the same direction. These twolines of the culturing modules are disposed in the internal space of theclosed structure 1 so that the front face openings in one line areopposite to the front face openings in another line. Moreover, a workspace in which one or more workers can work is formed between these twolines of the culturing modules. In order to improve the area utilizationrate and space utilization rate of the internal space of the closedstructure 1, it is preferable to form the work space as small and narrowas possible. When the culturing modules 3 to 6 are displaced in theclosed structure 1, a path of air passed through the culturing modulesis formed by providing a space having a width of about 50 to 300 mmbetween the inside wall face of the closed structure and the backs ofthe culturing modules.

Concerning internal dimensions of the closed structure 1 in the exampleshown in FIGS. 1 and 2, the width is 3,400 mm, the depth is 2,500 mm,and the height is 2,200 mm. Providing an air curtain at the inside of ahinged door 2 of an entrance is preferable because it is possible toprevent outside air from coming in when a worker passes through the door2.

The closed structure 1 is provided with an air conditioner having afunction for controlling the temperature and humidity of the air in theinternal space and circulating the air whose temperature and humidityhave been controlled to the predetermined conditions. Indoor units 7, 8,9, and 10 of the air conditioner are fixed to the upper portion of theinner face of the closed structure side wall and an outdoor unit (notillustrated) is positioned to the outside of the closed structure 1. Oneair conditioner may control the temperature and humidity of the wholeinternal space depending on the size of the closed structure. However,in order that the temperature-controlled and humidity-controlled air iseffectively circulated in the internal space of the closed structure 1,it is preferable to use a plurality of the indoor units of the airconditioner corresponding to the number of a plurality of the culturingmodules and fix each indoor unit to the upper portion of the inner faceof the closed structure side wall located at the rear of the back wallof each culturing module.

As shown in FIGS. 3 and 4, the culturing module 3 disposed in theinternal space of the closed structure 1 is provided with a boxy outershape having side walls 3 a and a back wall 3 b formed on the side andback faces thereof, respectively, and having a front face opening. Inthe culturing module 3, a plurality of culturing shelves 12 arevertically arranged in multi-layer at certain intervals, whereby thearea utilization efficiency of the transplant production space isimproved. It is preferable that the height of each culturing module 3 isset to about 2,000 mm at which a worker can work, the width of eachtransplant production shelf 12 is set to, for example, about 1,000 to2,000 mm at which a plurality of plug trays of synthetic resin eachhaving tens to hundreds of plugs (small pots) arrayed in a grid patterncan be mounted and the temperature and humidity in each shelf can becontrolled at a constant value, and the depth of each transplantproduction shelf 12 is set to 500 to 1,000 mm. Concerning externaldimensions of the culturing module 3 of the illustrated example, theheight is 1,650 mm, the width is 1,300 mm, and the depth is 650 mm andfour plug trays 40 (refer to FIG. 1) are mounted on each transplantproduction shelf 12. Concerning dimensions of one plug tray, the widthis about 300 mm and the length is about 600 mm in general.

A plurality of transplant production shelves 12 arranged in multi-layerin the culturing module 3 (four stages in the example shown in FIG. 3)are almost horizontal and a transplant production space is formedbetween the transplant production shelves 12. The transplant productionshelf located at the lowest-stage is mounted on a pedestal 3 c of theculturing module and the horizontality of the transplant productionshelves 12 can be adjusted by an adjuster 3 d set on the pedestal. Bydecreasing the interval between the adjacent transplant productionshelves and increasing the number of transplant production shelves, itis possible to improve the space utilization rate. However, when theinterval between the adjacent transplant production shelves is toosmall, there are disadvantages that the operability for removing orinserting plug trays is deteriorated and the maximum length of seedlingcannot be secured. Therefore, it is preferable that the interval is setto about 300 mm or more. The transplant production shelves 12 are formedpreferably by using metallic plates, metallic net, and metallic bars.

On each of the transplant production shelves 12 are mounted asub-irrigation unit to be described herein later and a plurality of plugtrays. Further, an artificial lighting unit 13 is provided on the backof each transplant production shelf 12 to irradiate light to plantsgrown in the plug trays of the transplant production shelf just belowthe lighting unit 13. In the case of the transplant production shelflocated at the highest-stage, the artificial lighting unit 13 isprovided on the back of the top wall 3 e of the culturing module.

A fluorescent lamp is preferable as the light source of the artificiallighting unit 13. It is possible to properly select the candlepower andlength of the fluorescent lamp in accordance with the width and lengthof the transplant production shelf 12 and the interval between theadjacent transplant production shelves 12. For example, when thetransplant production shelf having a width of 1,200 mm and a length of600 mm is used and the interval between adjacent transplant productionshelves is 350 mm, it is possible to attach four to eight fluorescentlamps each of which has a length of 1,200 mm and a candlepower of 32 to45 W in parallel on the back of each transplant production shelf.

As shown in FIG. 3, a plurality of air fans 15 are fixed to the backwall 3 b of each stage of the transplant production shelves 12. Byoperating the air fans 15, it is possible to generate air circulationflows shown by arrows in FIG. 2 in the internal space of the closedstructure 1. That is, the air whose temperature and humidity have beencontrolled by indoor units 7 to 10 of the air conditioner is sucked intothe transplant production space of each stage of the transplantproduction shelves 12 from the front face opening of each of theculturing modules 3 to 6, and discharged to the rear of the back wall ofeach culturing modules. The air discharged to the rear of the back wallof each culturing module is sucked into the indoor units 7 to 10 of theair conditioner, and, after the temperature and humidity of the air havebeen controlled, blown out to the front face openings of the culturingmodules 3 to 6. When two lines of the culturing modules 3 and 4 and theculturing modules 5 and 6 are arranged so that the work space is formedbetween them as in the example shown in FIGS. 1 and 2, the work spacefunctions concurrently as an air circulation path. Therefore, it ispossible to provide an effective circulation flow.

When the circulation flow passes through the transplant productionshelves 12 of the culturing modules 3 to 6, the circulation flow isaccompanied by water vapor evaporated from irrigation units, culturemedia and plant seedlings, and also by heat discharged from theartificial lighting units 13. By controlling the temperature andhumidity of the circulation flow using the indoor units 7 to 10 of theair conditioner and continuously circulating the flow, it is possible tokeep the internal space of the closed structure 1 at a temperature andhumidity environment optimum for plant growth.

When the width of each transplant production shelf 12 is small, one airfan 15 may be fixed to the back wall 3 b of each stage of the transplantproduction shelves. However, such a layout is not preferable because ofthe occurrence of uneven ventilation when a large width of thetransplant production shelf 12 is used. As shown in FIG. 3, by disposinga plurality of air fans 15 in each stage of the transplant productionshelf 12 (one air fan is disposed for each of four plug trays; total offour air fans in the example shown in FIGS. 1 and 3), it becomespossible to eliminate the uneven ventilation and uniform ventilation anduniform air circulation are realized. When a plurality of air fans aredisposed, it is allowed that the air suction force per one air fan iscomparatively small.

The sub-irrigation unit is mounted on each of the transplant productionshelves 12 arranged in multi-layer in the culturing modules 3 to 6 andemploys a system in which irrigation is carried out from the bottom ofthe plug trays mounted on each transplant production shelf. An exampleof the sub-irrigation unit is shown by a top view in FIG. 5, aperspective view in FIG. 6, and a sectional view in FIG. 7. Theillustrated sub-irrigation unit 30 is provided with a shallowquadrangular box-shaped irrigation tray 31 having three sides surroundedby side walls 31 a, 31 b and 31 c and a bottom wall face 31 d. Adrainage groove 32 jointed to the bottom wall face 31 d is formed at theside of the irrigation tray 31 having no side wall, and a drainage port32 a is formed at one end of the drainage groove 32. Further, a watersupply pipe 33 for supplying water (a culture solution containingfertilizer) into the irrigation tray 31 is also disposed. The watersupply pipe 33 may be disposed in any position as long as water can besupplied into the irrigation tray 31 from that position. In the case ofthe illustrated example, the water supply pipe 33 is disposed on theside wall 31 a of the irrigation tray opposite to the drainage groove 32and water is supplied from a plurality of small holes 33 a formed on thewater supply pipe. Moreover, the drainage groove 32 and the bottom wallface 31 d are partitioned by a dam 34 and a cutout 34 a is formed on apart (both ends in the case of the illustrated example) of the dam 34.

The sub-irrigation unit used in the present invention is characterizedin that means for holding a gap between the bottom wall face of theirrigation tray and the bottom of the plug tray is provided. The gap isheld at the time of mounting the plug tray on the bottom wall face ofthe irrigation tray. In the example shown in FIGS. 5 to 7, the gapholding means is constituted by a plurality of ribs 35 formed on thebottom wall face 31 d of the irrigation tray. The ribs 35 extend inparallel with each other to the direction of the drainage groove 32 andthe plug trays 40 are mounted on these ribs 35.

It is allowed that the irrigation tray 31 is made of a metal orsynthetic resin, the width and thickness of the irrigation tray 31 aresubstantially the same as those of the transplant production shelf 12arranged in each stage in the culturing modules 3 to 6, and the depth isset to about 30 to 50 mm. In the example of the illustratedsub-irrigation unit 30, the dimensions are such that the drainagegrooves 32 protrude from the front face openings of the culturingmodules at the time of mounting the irrigation trays 31 on thetransplant production shelves of the culturing modules 3 to 6 (refer toreference numeral 32 in FIG. 4). By protruding the drainage groove 32from the front face opening of the culturing module, water dischargedfrom the drainage port 32 a of the drainage groove 32 of the irrigationtray 31 mounted on each stage of the transplant production shelves 12 iseasily collected and drained to the outside of the closed structure 1.

When a predetermined quantity of water is continuously supplied from thesmall holes 33 a formed on the water supply pipe 33 of thesub-irrigation unit 30, the water is spread over the bottom wall face 31d of the irrigation tray and stopped by the dam 34 to thereby accumulateup to a predetermined water level and form a water pool state. Whilewater is supplied from the water supply pipe 33, water leaks little bylittle from the cutout 34 a (width of about 10 mm, for example) formedon the dam 34 into the drainage groove 32. However, by adjusting thesupplied water quantity and the water quantity leaking from the cutout,the pool state having a water level of about 10 to 12 mm can bemaintained in the irrigation tray 31. In this case, by narrowing thewidth of the cutout to decrease the outflow of the water, the suppliedwater quantity can be decreased and a small water supply pump may beused. When the pool state having such a water level as described aboveis maintained, water is soaked up, due to capillary action, to culturemedia in plugs 41 from plug holes 42 formed on bottoms of the plugs 41arrayed in the plug tray 40 mounted on the ribs 35 (average height ofabout 7 mm, for example) and thus the culture media in all of the plugs41 become a water saturated state in a short time. In addition, sincethe culture media in all of the plugs 41 arrayed in the plug tray 40become the water saturated state uniformly, it is unnecessary tocontinue irrigation any more. Thus, it is possible to apply uniformirrigation to all the plugs 41 of the plug tray 40 mounted on each stageof the transplant production shelves without accurately equalizing thewater quantity supplied to each stage of the transplant productionshelves 12.

When supply of water from the water supply pipe 33 is continued evenafter culture media in all the plugs of the plug tray become the watersaturated state, excess water is drained into the drainage groove 32.After automatically stopping the supply of water, although most of thewater in the irrigation tray 31 is drained in a short time to thedrainage groove 32 through the cutout 34 a formed on the dam 34, somewater remains on the bottom wall face 31 d of the irrigation tray toproduce a wet state. However, since the bottom of the plug tray 40 israised from the bottom wall face 31 d of the irrigation tray by means ofthe ribs 35, a gap is held between the bottom of the plug tray 40 andthe bottom wall face 31 d of the irrigation tray. By flowing thetemperature-controlled and humidity-controlled air through the gap, thevicinity of the plug holes 42 is made to be a dry state in a short time.

When the vicinity of the plug holes 42 formed at the bottom of the plugtray 40 is kept in a wet state, roots of seedling easily extend towardthe water. However, when the vicinity of the plug holes 42 is kept in adry state, roots of seedling do not extend in the direction of thelocation in the dry state. This phenomenon is referred to as air pruningeffect and denotes a state in which roots are pruned by using an airlayer as a boundary. According to the example of the sub-irrigation unit30 as shown in FIGS. 5 to 7 used for the transplant production system ofthe present invention, it is possible to securely bring the vicinity ofthe plug holes 42 into a dry state in a short time and positivelygenerate the air pruning effect. As a result, it is possible to preventroots of seedling from extending to the outside from the plug holes 42.Therefore, at the time of fix planting of the produced seedlings, thetakeout operation from the plugs 41 of seedling becomes easy and rootsare not damaged.

In the case of the example of the illustrated sub-irrigation unit 30, asshown by the sectional view in FIG. 7, the bottom wall face 31 d of theirrigation tray 31 is tilted in the direction of the drainage groove 32.Thereby, it is possible to drain water to the drainage groove 32 in ashort time when irrigation is stopped. Moreover, in the case where thebottom wall face 31 d is tilted, it is preferable to change heights ofthe ribs 35 so that the top surfaces 35 a of the ribs become horizontal,because the plug tray 40 mounted on the ribs can be kept horizontal.

FIG. 8 shows another example of the sub-irrigation unit used for thepresent invention. For omitting the description, the members same asthose in FIGS. 5 to 7 are designated by the same numerals. In thesub-irrigation unit 30′ as shown in FIG. 8, when the plug tray 40 ismounted on the bottom wall face 31 d of the irrigation tray, an lowertray 50 is intervened between the bottom wall face 31 d of theirrigation tray and the plug tray 40. The lower tray 50 has a rigiditycapable of supporting the plug tray 40 having the plugs 41 containingculture media, and is provided with a plurality of small holes 51 formedon the bottom wall thereof and a plurality of protrusions 52 attached tothe back face thereof. These protrusions 52 function as means forholding a gap between the bottom wall face 31 d of the irrigation trayand the bottom of the plug tray 40 when the plug tray 40 is housed inthe irrigation tray together with the lower tray 50.

Also in the sub-irrigation unit 30′ as shown in FIG. 8, when a waterpool state having a predetermined water level is realized by supplyingwater from the water supply pipe 33, water is introduced into the lowertray 50 from the small holes 51 of the lower tray 50 and water is soakedup to culture media in the plugs 41 from the plug holes 42 formed onbottoms of the plugs 41 of the plug tray 40 through capillary action.After stopping the supply of water from the water supply pipe 33, excesswater is drained to the drainage groove 32, and a small amount of waterremains on the bottom wall face 31 d of the irrigation tray. Even if thebottom wall face 31 d is in a wet state, the gap is held between thebottom of the plug tray 40 and the bottom wall face 31 d of theirrigation tray by the protrusions 52 on the back face of the lower tray50, and the temperature-controlled and humidity-controlled air flowsthrough the gap to thereby make the vicinity of plug holes 42 a drystate in a short time.

Also in the case of the example in FIG. 8, it is possible similarly tothe case of the example in FIGS. 5 to 7, to drain water to the drainagegroove 32 in a short time when irrigation is stopped, by tilting thebottom wall face 31 d of the irrigation tray in the direction of thedrainage groove 32.

The plug tray 40 mounted on the irrigation tray 31 of the sub-irrigationunits 30 and 30′ mounted on each stage of the transplant productionshelves 12 is formed by arraying tens to hundreds of plugs 41 in a gridpattern and integrating them into a tray shape. The width of one plugtray is 300 mm and its length is about 600 mm, and various types of plugtrays are commercially available. In general, the plug tray ismanufactured from a synthetic resin sheet by a forming method utilizingdifferential pressure. As the shape of the plug 41, an invertedfrustoconical shape is preferably employed and either of a circular coneor pyramid may be used. It is preferable to use a plug having a depth ofapproximately 15 to 50 mm and a capacity of approximately 4 to 30 ml andhaving a plug hole 42 in the bottom and capable of irrigation from thebottom.

In the case of the example of the transplant production system of thepresent invention shown in FIGS. 1 and 2, two lines of the total of fourculturing modules 3 to 6, that is, a line of two culturing modules 3 and4 and a line of two culturing modules 5 and 6, are arranged in theinternal space of the closed structure 1 so that the front face openingsin one line are opposed to the front face openings in the other line.Since the transplant production system of the present invention has astructure in which culturing modules are arranged in the internal spaceof the closed structure, it is possible to freely construct a transplantproduction system corresponding to a scale by properly selecting thesize of the closed structure and the number of culturing modules to bearranged in the closed structure. For example, FIG. 9 shows an examplein which two culturing modules 3 and 4 are disposed in the internalspace of the closed structure 1 so that they are arranged with theirfront face openings facing to the same direction. Further, FIG. 10 showsan example in which one culturing module 3 is disposed in the internalspace of the small closed structure 1. In FIGS. 9 and 10, the memberssame as those in FIGS. 1 and 2 are designated by the same numerals foromitting the description.

In the transplant production system of the present invention, it is notalways necessary to fix the indoor units 7 to 10 of the air conditionerinstalled in the closed structure 1 to the upper portion of the innerface of the side wall of the closed structure 1 located at the rear ofthe back wall of the culturing modules 3 to 6. The indoor units may befixed to any position as long as an air circulation flow can begenerated in the internal space of the closed structure by means of theindoor units of the air conditioner and the air fans 15 fixed to theback wall of the culturing modules. For example, as shown by the examplein FIG. 10, it is also possible to fix the indoor unit 7 of the airconditioner to the inner face of the side wall of the closed structure 1opposite to the front face opening of the culturing module 3.

Since the internal space of the closed structure has a highairtightness, in the case where the normal ventilation condition isapplied, it is necessary to artificially supply carbon dioxide gasconsumed through photosynthesis during culturing of seedlings.Therefore, as shown in FIG. 1, a liquid carbon dioxide cylinder 16 ispositioned in the outside of the closed structure 1 and a carbon dioxideanalyzer (not illustrated) is positioned in the inside of the closedstructure. It is possible to keep the carbon dioxide concentration inthe internal space at a predetermined value by a system for discharginga necessary amount of carbon dioxide from the carbon dioxide cylinder 16to the internal space of the closed structure in accordance with asignal sent from the carbon dioxide analyzer, when the carbon dioxideconcentration in the internal space of the closed structure measured bythe carbon dioxide analyzer becomes a certain value or less.

By culturing seedling in the internal space of the closed structureusing the transplant production system of the present invention, it ispossible to automatically control environmental conditions such asquantity of light, temperature, humidity, carbon dioxide and waterpreferable to culture seedling. In addition, since all the seedlings oneach of the transplant production shelves in the culturing modules withmulti-layer shelving can be cultured under the same environment, it ispossible to improve the uniformity of the obtained seedling quality. Theseedling quality here denotes external features such as length ofhypocotyl, diameter of hypocotyl, leaf color, leaf area and the like,and quality features such as forming position of floral bud, presence orabsence of bolting and the like.

INDUSTRIAL APPLICABILITY

According to the present invention described above, the followingadvantages can be obtained.

(1) By means of the indoor units of the air conditioner installed in theinternal space of the closed structure and the air fans fixed to theback walls of the culturing modules, it is possible to effectivelygenerate a circulation flow of temperature-controlled andhumidity-controlled air in the internal space. Therefore, installationof complex rectifying means is not required and efficient control oftemperature and humidity in the closed space can be carried out withminimum necessary power. As a result, it is possible to provide anenergy-saving and low-cost transplant production system.

(2) A circulation flow of temperature-controlled and humidity-controlledair can effectively be generated by a simple configuration in which theindoor units of the air conditioner and the air fans are disposed in theinternal space of the closed structure. Therefore, since it isunnecessary to form an air conditioning chamber, a blowing chamber, asuction chamber and the like in the internal space, a wide space forculturing seedling can be provided and as a result, the spaceutilization rate can be improved.

(3) By using the sub-irrigation unit having the dam formed on the bottomwall face of the irrigation tray, a water pool state having apredetermined water level can be easily realized. Thus, since culturemedia in all plugs of the plug tray can be brought into a watersaturated state in a short time by soaking up water from the bottom ofthe plugs, an amount of irrigation can be minimum necessary.

(4) By using the sub-irrigation unit providing with the gap holdingmeans between the bottom wall face of the irrigation tray and the bottomof the plug tray, a gap can be held between the bottom of the plug trayand the bottom wall face of the irrigation tray at the time of stoppingirrigation and the vicinity of the plug holes can be brought into a drystate by circulating the temperature-controlled and humidity-controlledair through the gap. As a result, it is possible to prevent roots ofseedling from extending from the plug holes to the outside and simplifythe operation for taking out seedling from the plug.

1. A system for transplant production comprising: at least one airconditioner installed in a completely light shielding closed structuresurrounded by a thermally insulated wall, the air conditionercontrolling the temperature and humidity of air in the closed structure;at least one box-shaped culturing module disposed in the internal spaceof the closed structure, the culturing module having a front faceopening which is opened to the internal space of the closed structure; aplurality of transplant production shelves arranged vertically inmulti-layer in the culturing module to form a transplant productionspace between the upper and lower transplant production shelves; aplurality of plug trays for holding a plant growing medium mounted oneach transplant production shelf; a sub-irrigation unit capable ofirrigation from the bottom of the plug trays mounted on each transplantproduction shelf; an artificial lighting unit provided on the back ofeach transplant production shelf, the artificial lighting unitirradiating light to the lower plug trays; and at least one air fanfixed to the back wall of each transplant production shelf of theculturing module, whereby the air whose temperature and humidity havebeen controlled by the air conditioner is sucked by the air fan from thefront face opening of the culturing module and sent to the rear of theback wall of each transplant production shelf to circulate the air inthe closed structure.
 2. The system for transplant production accordingto claim 1, wherein a plurality of the culturing modules are disposed inthe internal space of the closed structure so that they are arranged inone line with their front face openings facing to the same direction. 3.The system for transplant production according to claim 1, wherein aplurality of the culturing modules are arranged in two lines with theirfront face openings in the same line facing to the same direction, andthe front face openings in one line are opposed to the front faceopenings in the other line, and a work space and concurrently an aircirculation path is formed between the two lines of the culturingmodules.
 4. The system for transplant production according to claim 1,wherein the air conditioner is fixed to the upper portion of the innerface of the closed structure side wall located at the rear of the backwall of the culturing module.
 5. The system for transplant productionaccording to claim 1, wherein a carbon dioxide analyzer is positioned inthe inside of the closed structure and a carbon dioxide cylinder ispositioned in the outside of the closed structure so as to supply apredetermined amount of carbon dioxide into the closed structure fromthe carbon dioxide cylinder in accordance with an electrical signal sentfrom the carbon dioxide analyzer.
 6. The system for transplantproduction according to claim 1, wherein the sub-irrigation unit mountedon each transplant production shelf is provided with a shallowquadrangular box-shaped irrigation tray having three sides surrounded byside walls and having a bottom wall face, a water supply pipe forsupplying water into the irrigation tray is disposed in the irrigationtray, a drainage groove joined to the bottom wall face is formed at theside of the irrigation tray having no side wall, the drainage groove andthe bottom wall face are partitioned by a dam, and means for holding agap between the bottom wall face of the irrigation tray and the bottomof the plug tray is provided on the bottom wall face of the irrigationtray to thereby hold the gap at the time of mounting the plug tray onthe bottom wall face of the irrigation tray.
 7. The system fortransplant production according to claim 6, wherein the gap holdingmeans is constituted by a plurality of ribs formed on the bottom wallface of the irrigation tray so as to extend from the water supply pipeto the drainage groove.
 8. The system for transplant productionaccording to claim 6, wherein the gap holding means is constituted by aplurality of protrusions formed on the back of a perforated lower traypositioned between the bottom wall face of the irrigation tray and theplug tray at the time of mounting the plug tray on the bottom wall faceof the irrigation tray.
 9. The system for transplant productionaccording to claim 6, wherein at least one cutout is formed on the damof the irrigation tray.
 10. The system for transplant productionaccording to claim 6, wherein the bottom wall face of the irrigationtray gently tilts so that the drainage groove side lowers.